var ceng3zi = document.getElementsByClassName('ceng3zi');
var kuan2 = document.getElementsByClassName('kuan2');

for (let i = 0; i < ceng3zi.length; i++) {
    ceng3zi[i].onmouseover = function () {
        kuan2[i].style.display = 'flex';
    }
    ceng3zi[i].onmouseout = function () {
        kuan2[i].style.display = 'none';
    }
    kuan2[i].onmouseover = function () {
        kuan2[i].style.display = 'flex';
    }
    kuan2[i].onmouseout = function () {
        kuan2[i].style.display = 'none';
    }
}